The present invention relates to an ultrasonic Doppler diagnostic apparatus which measures the flow velocity information of a blood flow and the movement information of tissue in a living body by using the Doppler effect of ultrasonic waves, and a measuring method of diagnostic parameter.
An ultrasonic diagnostic apparatus is designed to apply ultrasonic pulses generated by piezoelectric transducers incorporated in an ultrasonic probe into an object to be examined, receive reflected ultrasonic waves generated by the difference in acoustic impedance between object tissues through the piezoelectric transducers, and display the resultant image on a monitor. This diagnostic method allows easy observation of a real-time two-dimensional image by simple operation of only bringing the ultrasonic probe into contact with the body surface, and hence is widely used for functional diagnosis or morphological diagnosis of various organs of a living body. Ultrasonic diagnostic methods of obtaining living body information by using reflected waves from tissue or blood cells in a living body have rapidly progressed along with two great technical developments of an ultrasonic pulse reflection method and ultrasonic Doppler method. B mode images and color Doppler images obtained by these techniques have become indispensable to recent ultrasonic image diagnosis.
A Doppler spectrum method is available as a method of obtaining blood flow information at an arbitrary position in an object quantitatively with high accuracy. In this Doppler spectrum method, ultrasonic wave transmission/reception is performed with respect to the same region of an object at predetermined intervals a plurality of number of times, and Doppler signals are detected by performing quadrature phase detection for reflected ultrasonic waves from moving reflectors such as blood cells by using a reference signal having a frequency almost equal to the resonance frequency of the piezoelectric transducers used for ultrasonic wave transmission/reception. A Doppler signal in the desired region is extracted from these Doppler signals by using a range gate. A Doppler spectrum is calculated by FFT-analyzing the extracted Doppler signal.
Doppler spectra are continuously calculated with respect to Doppler signals obtained from a desired region of an object by this sequence, and the plurality of obtained Doppler spectra are sequentially arrayed to generate Doppler spectrum data. In general, in order to accurately set a range gate at a desired observation region of an object, the range gate is set under B mode image observation. At this time, the range gate position is displayed on the B mode image.
The Doppler spectrum data obtained by this ultrasonic Doppler diagnostic apparatus is generally displayed with the ordinate representing a frequency (f), the abscissa representing time (t), and the power (intensity) of each frequency component being represented by a luminance (gray level). Various kinds of diagnostic parameters are measured on the basis of this Doppler spectrum data. For example, a maximum blood flow velocity Vp corresponding to a maximum frequency component fp in the frequency axis direction or the position of an average flow velocity Vc corresponding to an average frequency component fc is detected with respect to each of temporally continuously obtained Doppler spectra, and a trace waveform representing a temporal change in the maximum blood flow velocity Vp or average flow velocity Vc is generated.
When a blood flow in a blood vessel such as a carotid is to be evaluated, a waveform peak PS (Peak of Systolic) which occurs in a trace waveform in a systole and a waveform peak ED (End of Diastolic) which occurs in a diastole are detected. HR (Heart Rate) of an intravascular blood flow is measured on the basis of the position information of PS or ED. In addition, PI (Pulsatility Index), RI (Resistance Index), and the like as diagnostic parameters for a peripheral vessel are measured from a trace waveform in a cardiac cycle set by PS or ED.
Note that the generation of the trace waveform of Vp or Vc, the detection of PS/ED, and the measurement of a diagnostic parameter such as PI or RI, described above, are basically performed by manual operation with respect to frozen (freeze-displayed) Doppler spectrum data in the prior art. Recently, however, as disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 2003-284718, it has become possible that Vp or Vc be automatically traced or HR, PI, or RI be automatically measured with respect to Doppler spectrum data display in real time.